I have most of the packs with the exception of The Lost Realm and the following cycle up to The Sands of Harad. What I'm wondering is which is better insofar as player cards and/or the quests between The Sands of Harad and The Wilds of Rhovanion? I like thematic decks and quests and play mostly in multiplayer. Thanks!

Harad is complete so get it. Rhovanion will take a bit of time to be complete.

True, but expierencing a cycle develop has it's own charm (even though one should prepare for a long wait as release speed has dropped harshly).

While Harad had (for me) very fun quests, I don't remember very specific player cards (even though there surely were great ones)

Rhovanion introduces the Dale archetype, which utilizes a lot of ally attachments, and is a lot of fun to play. The quests are great so far, too!

So if you don't need a ton of quests right now, I'd suggest Rhovanion.

The Haradrim cycle gives support to already-established deck types and is completed and available

The Ered Mithrin cycle introduces quite a few new deck types and is mid-release.

Both have pros and cons. The quests are around the same level of enjoyment.

I share your love of thematic decks and quests, and based on that factor I'd definitely go for Rhovanian. There was always going to be more canon to work with than in Harad, but the choice to have a powerful, ready-made Dale deck in the deluxe box (and a Woodman archetype on the way) really doubled down on the theme. Add to that Thranduil and Grimbeorn heroes, the nostalgic revisiting of the Core Set, and the chance to fight dragons instead of more spiders, wargs and orcs in Harad (yawn) and Rhovanian's basically hitting all the spots that I felt Sands of Harad missed.

The Harrad are great and powerful, but in multiplayer (they are still good) but fall a bit off. Dale are fun to play, will still evolve and do shine in multiplayer.